1. Field of the Invention
The invention concerns a belt-driven conical-pulley transmission with a drive side and an output side conical disk pair.
2. Description of the Related Art
Belt-driven conical-pulley transmissions are recently increasingly being used in passenger cars. They not only make an increase in comfort possible, but also a decrease in fuel consumption. In order to expand the spectrum of use of belt-driven conical-pulley transmissions, intensive development efforts have been undertaken recently with respect to their capacity to transmit torque.
FIG. 5 depicts the upper half of a half section through an already known belt-driven conical-pulley transmission. A shaft 2 of a conical disk pair of a belt-driven conical-pulley transmission, which has an axis A—A, is preferably constructed in one piece with a fixed disk that is not represented. A conical disk designated as movable disk 6 is non-rotatably and axially displaceably arranged on the shaft 2 at a distance from the fixed disk. A support ring 8 is rigidly connected with the shaft 2 at a distance from the back side of movable disk 6, from which an axially oriented, cylindrical annular wall 10 projects in the direction toward conical disk 6 in a radially central region. An annular pot-like wall element 12 lies on or is attached on the radially outer area of the back side of the movable disk 6, which has radially inwardly and outwardly axially running, cylindrical annular walls 14 and 16. The inner annular wall 14 is in sealed off sliding contact with the annular wall 10, and the outer annular wall 16 is in sealed off sliding contact with the outer periphery of the support ring 8. In this way, an inner pressure chamber 22 is formed between the shaft 2 and the conical disk, as well as the annular walls 10 and 14, and an outer pressure chamber 26 is formed between annular walls 10, 14 and 16, as well as the floor 24 of the wall element 12 and the support ring 8.
The pressure medium supply of the inner pressure chamber 22 takes place through an axial passage 50 constructed in the shaft 2, which opens through a radial passage 28 of the shaft 2 into a space 30, which is constructed between the shaft 2 and the movable disk 6, and is connected with pressure chamber 22 through a passage 32 formed in movable disk 6. The axial length of the space 30 is such that a pressure medium connection exists between passage 28 and passage 32 over the entire adjustment path of the movable disk 6. The space 30 advantageously borders on a spline not represented in detail, through which the rotationally fixed and axially displaceable connection between movable disk 6 and the shaft 2 takes place.
The outer pressure chamber 26 is connected with an axial passage of shaft 2 through a channel 34 formed in the support ring 8, an annular channel 36 and a radial passage 38 formed in shaft 2, which is separated from the axial passage 50 that is connected with passage 28.
This way, the two pressure chambers 22 and 26 can be acted upon independently of each other by means of a pressure medium, so that the movable disk 6 can be moved in the direction of the not represented fixed disk.
A centrifugal oil chamber 40 is formed between the annular wall 16, a hood 42 lengthening the annular wall 16, and the back side of the support ring 8, which serves in an inherently known manner to compensate for rotational speed influences upon the pressures acting in chambers 22 and 26.
A problem in relation to the pressure medium supply of the inner pressure chamber 22 consists in that the passage 32 of movable disk 6 constructed as a transverse bore hole, or the space 30, which in accordance with FIG. 5 is sealed off merely through a single sealing gap toward the left of the not represented fixed disk, which is constructed between the outer periphery of shaft 2 and the inner periphery of conical disk 6. In practice this means comparatively high leakage losses, especially if the pressure in pressure chamber 22 is high.
To remedy this, the construction was somewhat modified. FIG. 6 illustrates an axial section through a conical disk pair of a modified belt-driven conical-pulley transmission, whereby in FIG. 6, the fixed disk 4 preferably constructed in one piece with the shaft 2 is also represented. Only the regions essential to the explained modification are provided with reference numbers in FIG. 6 for the sake of clarity.
As opposed to FIG. 5, the radially inner pressure chamber 22 formed in movable disk 6 is not supplied through a radial passage 32 formed in movable disk 6 in the entry region of a collar 44 of the movable disk 6 in the embodiment in accordance with FIG. 6, but the end region of the collar 44 of the fixed disk 6 facing the support ring 8 is provided with an overall radially running groove 46, whereby the geometrical arrangement is such that when the movable disk 6 is completely slid to the right in accordance with FIG. 6, groove 46 overlaps an overall radially running passage 48 of the shaft 2, so that a pressure medium connection between an axial passage 50 of the shaft and the pressure chamber 22 exists continuously.
The section C of FIG. 6 illustrates an embodiment, in which the groove 46 is constructed as a simple straight groove in the front end of the collar 44, which can already be forged or milled into the half-finished product of the conical disk 6.
A modified embodiment of the groove 46 is represented in the lower part of the image D, in which the groove 46 is constructed as an angle groove, the depth of which is radially inward directly great in reference to the diameter of the movable disk of the collar of the movable disk, or the collar of the movable disk, in order to assure the passage of the flow medium, and which is constructed with diminished depth towards the outside. In this way, the wear of the material is reduced.
Lower leakage losses to the intermediate space between the two conical disks 4 and 6 occur in the embodiment in accordance with FIG. 6 in comparison with the embodiment in FIG. 5, since, as is immediately apparent, the axial slot length to be penetrated by the flow is greater.
With higher mechanical loads of the movable disk 6 as they occur in connection with transmittable torques of, for example, over 350 Nm, the embodiments depicted no longer operate satisfactorily due to leakage losses and mechanical deformations and strains.